springBoot的过滤器，监听器，拦截器

2019 年 10 月 3 日
筆記

概述

　　在开发中，我们经常要考虑一些问题，对敏感词进行过滤，用户是否已经登录，是否需要对他的请求进行拦截，或者领导问现在在线人数有多少人？我们如何实现这些功能哪

@WebFilter

package com.xmlxy.firstspringbootproject;      import org.slf4j.Logger;  import org.slf4j.LoggerFactory;    import javax.servlet.*;  import javax.servlet.annotation.WebFilter;  import java.io.IOException;  @WebFilter(filterName = "customFilter",urlPatterns = "/*")  public class CustomFilter implements Filter {        private static final Logger log = LoggerFactory.getLogger(CustomFilter.class);        @Override      public void init(FilterConfig filterConfig) throws ServletException {          log.info("===========拦截器初始化==========");      }        @Override      public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {          servletRequest.setCharacterEncoding("utf-8");          servletResponse.setCharacterEncoding("utf-8");          log.info("doFilter请求处理");      }        @Override      public void destroy() {          log.info("fifter销毁");      }  }

在application类中添加@ServletComponentScan注解

package com;    import org.springframework.boot.SpringApplication;  import org.springframework.boot.autoconfigure.SpringBootApplication;  import org.springframework.boot.web.servlet.ServletComponentScan;  import org.springframework.context.annotation.PropertySource;    @SpringBootApplication  @ServletComponentScan  @PropertySource(value = "classpath:jdbc.properties",encoding = "utf-8")  public class FirstSpringbootProjectApplication {        public static void main(String[] args) {          SpringApplication.run(FirstSpringbootProjectApplication.class, args);      }    }

运行结果

（笔误，应该是过滤器初始化）过滤器已经生效，但若有多个过滤器，无法指定执行顺序，我们可以通过Java类的名称，从A-L，按顺序执行。但这种方式毕竟不大靠谱，所以，有第二种写法，它提供setOrder函数，为filter设置排序值。

package com.xmlxy.service;    import com.xmlxy.firstspringbootproject.CustomFilter;  import org.springframework.boot.web.servlet.FilterRegistrationBean;  import org.springframework.context.annotation.Bean;  import org.springframework.context.annotation.Configuration;    @Configuration  public class WebFilterConfig  {      @Bean      public FilterRegistrationBean someFilterRegistration1()      {          FilterRegistrationBean registration = new FilterRegistrationBean<>();          System.out.println("我执行了。。。。。。。");          registration.setFilter(new CustomFilter());          registration.addUrlPatterns("/*");

　　　　 registration.setOrder(1);

　　　　 return registration; } }

我们尝试写个demo，验证一下过滤器是否执行。

用户登录对象

User.java

package com.xmlxy.bean;    import lombok.Data;  import org.springframework.stereotype.Component;    @Data  @Component  public class User {      private String user;      private String pwd;  }

登录控制

LoginController.java

package com.xmlxy.firstspringbootproject;    import com.xmlxy.bean.User;  import org.springframework.web.bind.annotation.RequestMapping;  import org.springframework.web.bind.annotation.RequestMethod;  import org.springframework.web.bind.annotation.RestController;    import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpSession;    @RestController  public class LoginController {        @RequestMapping(value = "login",method = RequestMethod.GET)      public String login(HttpServletRequest request)      {          String user = request.getParameter("user");          String pwd = request.getParameter("pwd");          HttpSession session = request.getSession();          if ("admin".equals(user) && "admin".equals(pwd))          {              User user1 = new User();              user1.setUser(user);              user1.setPwd(pwd);              session.setAttribute("user",user1);              return "登录成功";          }          return "密码错误，登录失败";      }

　　@RequestMapping(value = "test",method = RequestMethod.GET)
　　public String test()
　　{
    　　return "test接口";
　　}

过滤器

CustomFilter.java

package com.xmlxy.firstspringbootproject;      import org.slf4j.Logger;  import org.slf4j.LoggerFactory;    import javax.servlet.*;  import javax.servlet.annotation.WebFilter;  import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;  import javax.servlet.http.HttpSession;  import java.io.IOException;  //@WebFilter(filterName = "customFilter",urlPatterns = "/*")  public class CustomFilter implements Filter {        private static final Logger log = LoggerFactory.getLogger(CustomFilter.class);        String includes[] = {"/login","register"};        @Override      public void init(FilterConfig filterConfig) throws ServletException {          log.info("===========过滤器初始化==========");      }        @Override      public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException      {          HttpServletRequest request = (HttpServletRequest) servletRequest;          HttpServletResponse response = (HttpServletResponse) servletResponse;          servletRequest.setCharacterEncoding("utf-8");          servletResponse.setCharacterEncoding("utf-8");          HttpSession session = request.getSession(false);          String uri = request.getRequestURI();          boolean flag = isNeedFilter(uri);          if (!flag)          {              filterChain.doFilter(servletRequest,servletResponse);              System.err.printf("登录成功");          }else {              if (session != null && session.getAttribute("user") != null)              {                  filterChain.doFilter(servletRequest,servletResponse);              }else {                  System.err.printf("暂时未登录");              }          }            log.info("doFilter请求处理");      }      public boolean isNeedFilter(String uri)      {          for (String include:includes)          {              if (include.equals(uri))              {                  return false;              }          }          return true;      }      @Override      public void destroy() {          log.info("fifter销毁");      }  }

过滤器配置

WebFilterConfig

package com.xmlxy.service;    import com.xmlxy.firstspringbootproject.CustomFilter;  import org.springframework.boot.web.servlet.FilterRegistrationBean;  import org.springframework.context.annotation.Bean;  import org.springframework.context.annotation.Configuration;    @Configuration  public class WebFilterConfig  {      @Bean      public FilterRegistrationBean someFilterRegistration1()      {          FilterRegistrationBean registration = new FilterRegistrationBean<>();          System.out.println("我执行了。。。。。。。");          registration.setFilter(new CustomFilter());          registration.addUrlPatterns("/*");          return registration;      }  }

运行测试。。访问 127.0.0.1/test 控制台

访问 http://127.0.0.1:8080/login?user=admin&pwd=admin，可以看到登录成功

在次访问 127.0.0.1/test 页面显示

所以，我们的过滤器成功过滤未登录的用户

监听器

正在你为自己会了过滤用户自鸣得意时，你的组长过来了，小明，你看下我们平台的在线用户有多少人。如果不知道监听器童鞋，是否会在登录接口处每次登录成功都+1，然而这种统计结果是不准确的，因为用户如果反复登录退出，那这个在值就远远大于实际值，最后就面临着，加班在加班的悲惨下场。

CustomLister.java

package com.xmlxy.firstspringbootproject;      import javax.servlet.annotation.WebFilter;  import javax.servlet.http.HttpSessionEvent;  import javax.servlet.http.HttpSessionListener;    @WebFilter  public class CustomLister implements HttpSessionListener  {      public static int online = 0;        @Override      public void sessionCreated(HttpSessionEvent sessionEvent)      {          System.out.println("创建session,统计在线人数");          online ++;      }        @Override      public void sessionDestroyed(HttpSessionEvent sessionEvent)      {          System.out.println("session已经销毁");      }  }

配置监听器配置,在刚才的WebFilterConfig.java添加

@Bean      public ServletListenerRegistrationBean listenerRegistrationBean()      {          ServletListenerRegistrationBean srb = new ServletListenerRegistrationBean();          srb.setListener(new CustomLister());          System.out.println("");          return srb;      }

添加一个访问在线人数的接口

@RequestMapping(value = "onLinePerson",method = RequestMethod.GET)      public String onLinePerson()      {          StringBuffer stringBuffer = new StringBuffer("");          stringBuffer.append(" 在线人数 ");          stringBuffer.append(CustomLister.online);          stringBuffer.append(" 个人 ");          return stringBuffer.toString();      }

访问127.0.0.1/onLinePerson,发现被拦截器拦截了，我们先登录。在查看接口

换个浏览器，调用下login接口，在查看

拦截器

拦截器，个人理解，在web上有些像是过滤器的补充，它能更精确的控制拦截哪些函数或者字段，在拦截之前或之后做一些操作。我们现在做一个敏感词的拦截，其实这个操作放在过滤器操作也是可以的，但lz因为刚才把拦截用户的操作放在过滤器了，在大规模更改，lz觉得没必要，因为都是大同小异。

CustomInterceptor.java

package com.xmlxy.firstspringbootproject;    import org.slf4j.Logger;  import org.slf4j.LoggerFactory;  import org.springframework.web.servlet.HandlerInterceptor;  import org.springframework.web.servlet.ModelAndView;  import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;  import java.io.PrintWriter;    public class CustomInterceptor implements HandlerInterceptor  {      private static final Logger log = LoggerFactory.getLogger(CustomInterceptor.class);      @Override      public boolean preHandle(HttpServletRequest request, HttpServletResponse response,Object handler) throws Exception {          log.info("=======拦截器被调用=====");          String url = request.getRequestURI();          if (url != null && url.indexOf("seqing") != -1)          {              PrintWriter printWriter = response.getWriter();              printWriter.write("ming gan ci");              return false;          }          log.info("返回false 则中断请求");          return true;      }        @Override      public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)      {          log.info("请求后调用");      }        @Override      public void afterCompletion(HttpServletRequest request,HttpServletResponse response,Object handler,Exception e)      {          log.info("视图渲染完回调");      }  }

配置拦截

package com.xmlxy.service;    import com.xmlxy.firstspringbootproject.CustomFilter;  import com.xmlxy.firstspringbootproject.CustomInterceptor;  import com.xmlxy.firstspringbootproject.CustomLister;  import org.springframework.boot.web.servlet.FilterRegistrationBean;  import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;  import org.springframework.context.annotation.Bean;  import org.springframework.context.annotation.Configuration;  import org.springframework.web.servlet.config.annotation.InterceptorRegistry;  import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;    @Configuration  public class WebFilterConfig implements WebMvcConfigurer  {      @Bean      public FilterRegistrationBean someFilterRegistration1()      {          FilterRegistrationBean registration = new FilterRegistrationBean<>();          System.out.println("我执行了。。。。。。。");          registration.setFilter(new CustomFilter());          registration.addUrlPatterns("/*");          return registration;      }        @Bean      public ServletListenerRegistrationBean listenerRegistrationBean()      {          ServletListenerRegistrationBean srb = new ServletListenerRegistrationBean();          srb.setListener(new CustomLister());          return srb;      }        @Override      public void addInterceptors(InterceptorRegistry registry)      {          /*拦截规则*/          registry.addInterceptor(new CustomInterceptor()).addPathPatterns("/*");      }    }

现在测试访问127.0.0.1/seqing，被过滤，要求先登录。我们调用登录接口后，再次调用，发现被拦截了

看下日志调用，可以发现，拦截器是在访问接口前被调用的

过滤器，拦截器区别

这里主要说下拦截器和过滤器的区别和使用场景，通过demo可以发现，它们都能实现权限的检查，日志记录这些功能，主要说下它们的区别

过滤器和拦截器触发的时机是不同的，在进入servlet之前，过滤器就进行预处理了。而拦截器是在调用Controller之前才触发执行，过滤器的范围较广，对所有的请求都起作用，而拦截起只对action起作用

　　2.拦截器可以获取IOC容器的各个bean，而过滤器就不行。因为拦截器是spring提供管理的，也因此拦截器可以使用spring的任何资源。

　　3.拦截器是利用Java反射机制实现，过滤器是函数的回调。因此实现方式是不同的。

三者使用场景

　　监听器：常用统计在线用户，统计网站的访问量，记录用户的访问路径

　　过滤器：过滤敏感词，权限访问控制

　　拦截器：权限验证，判断用户是否登录等